linux-kernel - Re: [PATCH v2 3/3] media: mt9m111: don't turn on the output while powering it

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Message-ID: <20220919131703.iuooxq4flk7d7353@pengutronix.de>
Date:   Mon, 19 Sep 2022 15:17:03 +0200
From:   Marco Felsch <m.felsch@...gutronix.de>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     mchehab@...nel.org, sakari.ailus@...ux.intel.com,
        akinobu.mita@...il.com, jacopo+renesas@...ndi.org,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] media: mt9m111: don't turn on the output while
 powering it

Hi Laurent,

On 22-09-19, Laurent Pinchart wrote:
> Hi Marco,
> 
> Thank you for the patch.
> 
> On Fri, Sep 16, 2022 at 03:57:13PM +0200, Marco Felsch wrote:
> > Currently the .s_power() turn on/off the device and enables/disables the
> > sensor output. This is wrong since it should only handle the power not
> > not the sensor output behaviour. Enabling the sensor output should be
> > part of the .s_stream() callback.
> > 
> > Fix this by adding mt9m111_set_output() which gets called by the
> > .s_stream() callback and remove the output register bits from
> > mt9m111_resume/suspend.
> > 
> > Signed-off-by: Marco Felsch <m.felsch@...gutronix.de>
> > ---
> > Changelog:
> > 
> > v2:
> > - new patch, replaces: "media: mt9m111: remove .s_power callback"
> > ---
> >  drivers/media/i2c/mt9m111.c | 38 ++++++++++++++++++++++++++-----------
> >  1 file changed, 27 insertions(+), 11 deletions(-)
> > 
> > diff --git a/drivers/media/i2c/mt9m111.c b/drivers/media/i2c/mt9m111.c
> > index 8de93ab99cbc..2cc0b0da7636 100644
> > --- a/drivers/media/i2c/mt9m111.c
> > +++ b/drivers/media/i2c/mt9m111.c
> > @@ -426,10 +426,25 @@ static int mt9m111_setup_geometry(struct mt9m111 *mt9m111, struct v4l2_rect *rec
> >  	return ret;
> >  }
> >  
> > -static int mt9m111_enable(struct mt9m111 *mt9m111)
> > +static int mt9m111_set_output(struct mt9m111 *mt9m111, int on)
> >  {
> >  	struct i2c_client *client = v4l2_get_subdevdata(&mt9m111->subdev);
> > -	return reg_write(RESET, MT9M111_RESET_CHIP_ENABLE);
> > +	int ret;
> > +
> > +	if (on) {
> > +		ret = reg_clear(RESET, MT9M111_RESET_OUTPUT_DISABLE);
> > +		if (ret)
> > +			return ret;
> > +
> > +		return reg_set(RESET, MT9M111_RESET_CHIP_ENABLE);
> > +	}
> > +
> > +	/* disable */
> > +	ret = reg_set(RESET, MT9M111_RESET_OUTPUT_DISABLE);
> > +	if (ret)
> > +		return ret;
> > +
> > +	return reg_clear(RESET, MT9M111_RESET_CHIP_ENABLE);
> 
> Unless the hardware specifically requires this sequence, I'd use the
> inverse of the enable sequence here.

Output-disable: -> put output pins into tri-state.
chip-enable:  -> reset sensor readout path.

Enable:
  -> set output pins accordingly
     -> put sensor out of reset --> start sensor readout

Disable:
  -> set output pins to tri-state
     -> put sensor into reset --> stop sensor readout

To avoid possible artifacts I disabled the pins first before resetting
the sensor core (stopping the readout).

Regards,
  Marco

> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> 
> >  }
> >  
> >  static int mt9m111_reset(struct mt9m111 *mt9m111)
> > @@ -927,10 +942,7 @@ static int mt9m111_suspend(struct mt9m111 *mt9m111)
> >  	ret = reg_set(RESET, MT9M111_RESET_RESET_MODE);
> >  	if (!ret)
> >  		ret = reg_set(RESET, MT9M111_RESET_RESET_SOC |
> > -			      MT9M111_RESET_OUTPUT_DISABLE |
> >  			      MT9M111_RESET_ANALOG_STANDBY);
> > -	if (!ret)
> > -		ret = reg_clear(RESET, MT9M111_RESET_CHIP_ENABLE);
> >  
> >  	return ret;
> >  }
> > @@ -951,9 +963,9 @@ static void mt9m111_restore_state(struct mt9m111 *mt9m111)
> >  
> >  static int mt9m111_resume(struct mt9m111 *mt9m111)
> >  {
> > -	int ret = mt9m111_enable(mt9m111);
> > -	if (!ret)
> > -		ret = mt9m111_reset(mt9m111);
> > +	int ret;
> > +
> > +	ret = mt9m111_reset(mt9m111);
> >  	if (!ret)
> >  		mt9m111_restore_state(mt9m111);
> >  
> > @@ -965,9 +977,7 @@ static int mt9m111_init(struct mt9m111 *mt9m111)
> >  	struct i2c_client *client = v4l2_get_subdevdata(&mt9m111->subdev);
> >  	int ret;
> >  
> > -	ret = mt9m111_enable(mt9m111);
> > -	if (!ret)
> > -		ret = mt9m111_reset(mt9m111);
> > +	ret = mt9m111_reset(mt9m111);
> >  	if (!ret)
> >  		ret = mt9m111_set_context(mt9m111, mt9m111->ctx);
> >  	if (ret)
> > @@ -1116,8 +1126,14 @@ static int mt9m111_enum_mbus_code(struct v4l2_subdev *sd,
> >  static int mt9m111_s_stream(struct v4l2_subdev *sd, int enable)
> >  {
> >  	struct mt9m111 *mt9m111 = container_of(sd, struct mt9m111, subdev);
> > +	int ret;
> > +
> > +	ret = mt9m111_set_output(mt9m111, enable);
> > +	if (ret)
> > +		return ret;
> >  
> >  	mt9m111->is_streaming = !!enable;
> > +
> >  	return 0;
> >  }
> >  
> 
> -- 
> Regards,
> 
> Laurent Pinchart
>